I'm looking for some fresh ideas 'cause I'm exhausted. This beautiful machine has failed NOx at 1400 ppm at 15 mph with a cut point of 778 ppm. It has 37,000 miles on the clock, 5.7L 32 valve DOHC with 16 injectors. Tailpipe readings show CO2 13.7%, O2 1.31%, ... Login to read more.